Season 4

Week one's challenges are heavily focused on the "exploration" theme. Jonathan's challenge is to make a rover; a remote controlled vehicle that could explore strange new worlds. Staying with the theme of exploration, Iain and Ellen have to use their geological and botanical skills to search for water in the desert. Assuming they find some water, Kathy and Mike are going to have to find a way of purifying it to make it safe for drinking and they're going to have to make it taste good as well, because at the end of day three Kathy and Mike's purified water will be up against drinking water.

No space mission can succeed without communication, so our second set of Rough Science space challenges are all based around making contact. Jonathan and Kathy have to come up with a way of communicating that doesn't use sound waves - because in the vacuum of space, there's nothing for them to move through. It took two years and a million pounds to develop a pen for use in space - one that would work in zero gravity. Ellen and Mike have no money and just three days to come up with their own version. Iain's challenge is very different. He has to find a way to communicate with aliens!

Although everyone thinks of space as very cold, in fact, if you stood on the sunny side of the moon, the temperature would be hot enough to boil the blood in your body. Spacesuits are designed to protect astronauts from these extremes of temperature. So for this week's challenge the Rough Scientists have to collectively design a cooling system for their very own spacesuit. And to test it out, at the end of day three, they're going to have to go to Death Valley and do a mock moon walk in their spacesuit - hopefully staying deliciously cool. They decide that they need to make a portable Rough Science fridge. Ellen creates a copper pipe system that will go from the fridge to the spacesuit, carrying cool water from the fridge to the astronaut. Jonathan devises a pump to keep the water moving through the system. Kathy suggests that the fridge should use the principle of evaporation - the same principle that cools us when we sweat. She needs to get water evaporating inside the fridge. And the best way to do that is to lower the pressure; this speeds up evaporation and therefore cooling. But there's a problem - all that evaporating water is trapped inside the fridge, and unless they can get it out then it will destroy the vacuum. Fortunately there's a magic mineral called zeolite that has a special property - it absorbs water vapour. So if they can find zeolite and put it in the fridge it will suck up the water vapour, preserving the vacuum. Mike attempts to extract zeolite from washing powder, whilst Iain tries to find naturally occurring zeolite in the rocks around the mine. So at the end of day three the Rough Scientists decamp to Death Valley where Ellen is dressed in their spacesuit for a spacewalk which will reveal whether their cooling system really can keep someone cool in one of the hottest places on Earth.

This week's programme is all about meteorites and asteroids. Not too far from the Rough Science base on the edge of Death Valley is Meteor Crater. Iain, Kathy and Mike have to work out how big the meteor that caused this huge crater must have been. But it's not just the Earth that gets hit by objects from outer space - the moon is also a target, as evidenced by its heavily cratered surface. So Jonathan and Ellen have to pick a crater on the moon - any crater will do - and measure how big it is. And because they'll be doing their measurements at night, Ellen has to come up with some lights. The Meteor Crater team decide they have to split their work. Kathy and Iain head off to the crater itself to try and measure its diameter. This is the first essential step if they are to work out how big the meteor was that caused the crater. At the same time, they are hoping to find out more about the meteor in the hope this will give them clues about its size. Meanwhile Mike stays behind to try and make his own crater. He performs a series of impact experiments, dropping heavy objects into sand in an effort to work out the relationship between the size of an object and the size of crater it forms. Jonathan and Ellen have been given a high quality optical mirror, and so to find and measure a crater on the moon, they build a reflecting telescope. Their plan is to time how long it takes the whole moon to travel across a fixed point in their eyepiece, and then time how long it takes their chosen crater to travel across that same fixed point. Because they know that the moon is 3500 kilometres across, they can use this as a starting point to calculate the diameter of the crater. For her lights Ellen heads to the hills and collects pine sap. She melts it to remove some of the most volatile compounds, and then uses bark fibres as wicks, to make highly effective Rough Science candles.

In Programme One the Rough Scientists had to make a Mars Rover which could explore strange new worlds. This week Kathy and Jonathan have to go one better and design an aerial surveyor that can explore much greater areas by floating above land. Just like the rover challenge, they've been given a tiny camera which will record whatever the aerial surveyor sees. Back on Earth, Mike has a very different challenge. Back in 1970 the crew of Apollo XIII faced certain death when an accident damaged their oxygen tanks. To survive they had to build a carbon dioxide filter - and Mike has to do the same. In 1872 California experienced one of the biggest earthquakes ever recorded in the United States. Ellen and Iain have to work out where the epicentre of the quake was, and its magnitude. Kathy and Jonathan decide to make a solar balloon - heated by the power of the sun. Made by sticking black bin bags together, the idea is to hang the camera below it. (An idea, incidentally, that NASA are actively exploring for Mars.) Unfortunately the Rough Science version encounters a series of unexpected setbacks, and on Day Three it is touch and go whether it will get off the ground. For Mike to make his carbon dioxide filter he needs to make limewater. To do that he needs to find limestone, heat it up to make quicklime, and then dissolve it in water. However, making quicklime proves to be more difficult than anticipated, and on Day Three he faces a classic Rough Science test to see if he has succeeded in making a working carbon dioxide filter. Ellen and Iain take to the air to try and find the site of the 1872 earthquake. Their first task is to find the fault line which marks the location of the earthquake. They then set out to measure the amount of movement that occurred along the fault, to work out where the maximum displacement was. This should give them the epicentre of the earthquake, and also provide the information they need to calculate its magnitude. Should - but will it?

Our final set of Rough Science space challenges are all about rockets. Mike, Jonathan and Kathy have to make three different rockets, but there's a catch; they're only allowed to use one thing as a fuel - and that's water! They've also got to design their rockets to carry a "passenger" - a (raw) egg. And Ellen and Iain have to find a way of returning the egg safely to Earth. Each of our 3 rocketeers designs a rocket that fits their science background. Jonathan's is the most ambitious - his physics background inspires him to build a steam powered rocket. Kathy - also a physicist - decides to use pressurised water, and Mike takes a chemical approach, using electrolysis to split water into hydrogen and oxygen gases, and then recombining them to form an explosive mixture. (Hydrogen and oxygen are what NASA uses to fuel its rockets - but the difference is that NASA uses a liquid fuel which can compress far more energy into a much smaller space.) What develops is a Rough Science space race, as the scientists compete to see who can get to the launch pad first, and whose rocket will be the most effective. Meanwhile, Ellen and Iain have to find a way of putting an egg on each rocket and returning it to Earth. They opt for a parachute made out of bin bags, and design a detachable nosecone for the rockets. However, the "detachable" part proves harder to achieve than first thought...